The latest scandal to hit U.S. troops fighting in Afghanistan surfaced last week when The Los Angeles Times published photographs showing smiling American soldiers holding up body parts of a Taliban suicide bomber.

U.S. Defense Secretary Leon Panetta addressed the latest incident during a trip to Brussels.

"That behavior that was depicted in those photos absolutely violates both our regulations and, more importantly, our core values," he said last week after a NATO meeting.

Senior military leaders say these high-profile incidents — including images of Marines urinating on the corpses of dead insurgents and other Marines posing with a Nazi SS flag — are isolated and not representative of the vast majority of those serving in Afghanistan.

Still, senior officers are asking, after 10 years of grinding war, whether leaders of small units are maintaining the proper standards of conduct.